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1. ### Change guitar string tension and vibration

Change in guitar string tension - Please help? Homework Statement A particular guitar string is supposed to vibrate at 220 Hz, but it is measured to actually vibrate at 225 Hz. By what percentage should the tension in the string be changed to get the frequency to the correct value? Do not...
2. ### Forced Oscillator where Damping is Negligible

Ahh, yes, I see what I did. I did mess up the algebra without noticing. I had it straight in my head but not on paper. Thank you very much for pointing that out for me. I've got the correct answer now.
3. ### Finding Frequency of an Oscillating Disc with a Hole

I realized that not long after I asked. I'm now assuming it's a trick question. 0 is the correct answer. I think it was trying to show that because distance from the center of mass was zero, all the rest was zero as well.
4. ### Finding Frequency of an Oscillating Disc with a Hole

Homework Statement A circular disk with a rectangular hole has a radius of 0.600 m and mass of 0.390 kg. It is suspended by a point on its perimeter as shown in the figure. The moment of inertia about this point is I_p = 2.60E-1 kgm2. Its center of mass is located at a distance of s=0.120 m...
5. ### Forced Oscillator where Damping is Negligible

How? I did the following: √((ω^2 - ωo^2)^2) Shouldn't the square root and the square cancel, leaving (ω^2 - ωo^2) ω^2 - (√k/m)^2 ω^2 - (k/m) Resulting in: ω^2 = √((Fo/m)/A) + (k/m) Where did I go wrong?
6. ### Forced Oscillator where Damping is Negligible

Homework Statement Damping is negligible for a 0.139 kg mass hanging from a light 7.00 N/m spring. The system is driven by a force oscillating with an amplitude of 1.88 N. At what frequency will the force make the mass vibrate with an amplitude of 0.430 m? There are two possible solutions...
7. ### Upward Acceleration of a Hanging Mass Connected to Another By a Pulley

I have no idea. I'll try to work this out in the morning. It's getting pretty late here too. Goodnight! Thank for the advice. I'll take that into account when I try again.
8. ### Force of a hinge on a hinged beam

Okay, I understand that I need to use cos instead of sin, but I still don't understand what to do without the length of the beam.
9. ### Upward Acceleration of a Hanging Mass Connected to Another By a Pulley

Would it be τ = (T1-T1)rsinθ then? What else is wrong?
10. ### Upward Acceleration of a Hanging Mass Connected to Another By a Pulley

Yes, that does make sense. Where else did I go wrong here?
11. ### Upward Acceleration of a Hanging Mass Connected to Another By a Pulley

Shouldn't T2 be equal to m2's weight plus the effect the acceleration of the system has on it? It doesn't make sense to me for it to be only the weight of gravity since the system is accelerating left.
12. ### Upward Acceleration of a Hanging Mass Connected to Another By a Pulley

I worked it through with the guy that runs the math help center. To be honest, even I'm confused by my own workings. But as for symbols, I use alpha for angular acceleration, a for linear acceleration, and g for acceleration due to gravity. I think I need to start this question over from...
13. ### Rotating Space Station

:redface: Do you ever have one of those moments where you just can't believe you mixed up something really simple? Thank you very much for pointing that out. I feel a bit foolish, but I do have the right answer now.
14. ### Force of a hinge on a hinged beam

Homework Statement A 26.6 kg beam is attached to a wall with a hinge and its far end is supported by a cable. The angle between the beam and the cable is 90°. If the beam is inclined at an angle of theta=13.3° with respect to horizontal, what is the horizontal component of the force exerted...
15. ### Rotating Space Station

I tried both, but when whittled down to the required three sigfigs, the answer is still 0.398 rad/s. I'm at a loss as to what to do differently.
16. ### Rotating Space Station

Homework Statement A proposed space station includes living quarters in a circular ring 62.0 m in diameter. At what angular speed should the ring rotate so the occupants feel that they have the same weight as they do on Earth? The attempt at a solution I assumed that to do this...
17. ### Calculating moment of inertia about a door hinge.à

Got it! Thanks!
18. ### Calculating moment of inertia about a door hinge.à

So to get velocity, I take the linear velocity and multiply it by the width of the door to get ω, and then plug that value into the energy equation? Edit: when I do that I get 30.6 J and that is incorrect.
19. ### Calculating moment of inertia about a door hinge.à

Oh! Okay. How do I calculate angular speed from tangential speed?
20. ### Calculating moment of inertia about a door hinge.à

I have the answer to the first question, but I'm not nearly as well off with the second question as I had assumed. I got 37 kgm^2 for the first question. I assumed you would take that value and take 76.5 cm/s (.765 m/s) as ω and plug it into E = (1/2)Iω^2 I get 10.8 when I do that (I...
21. ### Two Masses Hanging on a Massive Pulley

The following are my incorrect answers: 1 Incorrect. (Try 1) GLETLE 2 Incorrect. (Try 2) GEETLE 3 Incorrect. (Try 3) GEETLL 4 Incorrect. (Try 4) GLETLL 5 Incorrect. (Try 5) GGLFLL 6 Incorrect. (Try 6) GGEFLL
22. ### Two Masses Hanging on a Massive Pulley

So T2 is greater than T1? Okay. So, would a-G b-G c-E d-T e-L f-L sound right?
23. ### Calculating moment of inertia about a door hinge.à

Homework Statement A solid door of mass 39.30 kg is 2.34 m high, 1.68 m wide, and 3.23 cm thick. What is the moment of inertia of the door about the axis through its hinges? If the edge of the door has a tangential speed of 76.5 cm/s, what is the rotational kinetic energy of the door...
24. ### Two Masses Hanging on a Massive Pulley

But why? Am I missing a law or something?
25. ### Solving SHM: Max Speed & Accel. for 1.11kg Mass on Spring

I was missing those equations in my notes. I've got the answers now. Thank you very much!
26. ### Two Masses Hanging on a Massive Pulley

Homework Statement A pulley with mass Mp and a radius Rp is attached to the ceiling, in a gravity field of 9.81 m/s2 and rotates with no friction about its pivot. Mass M2 is larger than mass m1. The quantities Tn and g are magnitudes. (image attached) Select T-True, F-False, G-Greater than...
27. ### Find Acceleration At Time t For Mass on a Spring

I have the answer now. Thank you!
28. ### Solving SHM: Max Speed & Accel. for 1.11kg Mass on Spring

Homework Statement A mass of 1.11 kg on a spring rests on a frictionless surface and has a horizontal force of magnitude 1.23 N applied to it to keep it 1.3 m from the equilibrium. The mass undergoes simple harmonic motion when released. What is the maximum speed? What is the maximum...
29. ### Upward Acceleration of a Hanging Mass Connected to Another By a Pulley

Homework Statement A 26.3 kg block (m1) is on a horizontal surface, connected to a 7.10 kg block (m2) by a massless string as shown in the figure below. The frictionless pulley has a radius R = 0.060 m and a moment of inertia I=0.090 kgm2. A force F = 220.1 N acts on m1 at an angle theta =...
30. ### Find Acceleration At Time t For Mass on a Spring

Homework Statement A mass is oscillating on a spring with a period of 4.35 s. At t = 0 the mass has zero speed and is at x = 3.25 cm. What is the magnitude of the acceleration at t = 1.30 s? The attempt at a solution The formula for oscillatory acceleration is a(t) = -Aω^2cos(ωt - ∅)...
31. ### Pivoting Sledgehammer

I've finally got it! Thank you so very much!
32. ### Pivoting Sledgehammer

Alright, so, Ip = Icm +mr^2 Ip = 0.039 + (2.3 x 0.57^2) Ip = 0.78627 Plugging that into the E1 = E2 business earlier, I get w = 4.157 rad/s Then v = wr, v = 2.37 m/s And again it is incorrect. I honestly have no idea how to move forward.

Thank you!
34. ### Pivoting Sledgehammer

Oh, okay. But I end up with 11.7, which is still the incorrect answer.
35. ### Air-Track Cart Oscillating on a Spring, solve for time

Homework Statement The position of a an air-track cart that is oscillating on a spring is given by (14.0cm)cos[(12.0s-1)t]. At what value t after t=0 is the cart first located at x=2.0 cm? The attempt at a solution y = Acos(wt+∅) y = 14cos(12t) 2 = 14cos(12t) (1/7) = cos(12t)...
36. ### Pivoting Sledgehammer

v = wr so, with the angular speed I have, v = (20.568)(0.570) v = 36.1 m/s Which is incorrect. Where am I going wrong?
37. ### Pivoting Sledgehammer

Homework Statement [/b] A sledgehammer with a mass of 2.30 kg is connected to a frictionless pivot at the tip of its handle. The distance from the pivot to the center of mass is r_cm=0.570 m, and the moment of inertia about the center of mass is I_cm = 0.0390 kgm2. If the hammer is released...

Have you covered momentum yet? I don't remember how to calculate force of thrust without using momentum, so I hope this is helpful to you. The equation for Force of Thrust I know, is F(thrust) = ((m * V)2 - (m * V)1) / (t2 - t1) This can also be written as F(thrust) = Δp / Δt Force of thrust...
39. ### Impulse of Soccer Ball on Head

Okay, I think I understand how to do that now. My prof and I must have misunderstood the question. Thank you! Got it! Thanks! I don't know why it didn't register to me that since it was an isosceles triangle I could use another method to find the base. Thank you.
40. ### Impulse of Soccer Ball on Head

Homework Statement Recent studies have raised concern about 'heading' in youth soccer (i.e., hitting the ball with the head). A soccer player 'heads' a size 5 ball deflecting it by 31.0°, and keeps its speed of 10.40 m/s constant. A size 5 ball has a mass of approximately 0.446 kg. What is the...
41. ### Mass Slides Inside a Hoop

Okay. I'm forgetting the force of gravity acting on the mass, aren't I? Should I add mgcosθ to my answer? Is that all I'm missing?
42. ### Block Collides With Horizontal Spring

Homework Statement A moving 2.40 kg block collides with a horizontal spring whose spring constant is 478 N/m. The block compresses the spring a maximum distance of 13.00 cm from its rest position. The coefficient of kinetic friction between the block and the horizontal surface is 0.360...
43. ### Dart Fired from a Dart Gun

Homework Statement I need help with the very last of a series of questions: The potential energy stored in the compressed spring of a dart gun, with a spring constant of 66.00 N/m, is 0.76 J. Find by how much is the spring is compressed. My correct answer: 0.152 m A 0.190 kg dart is...
44. ### Mass Slides Inside a Hoop

Homework Statement A mass M of 5.20E-1 kg slides inside a hoop of radius R=1.40 m with negligible friction. When M is at the top, it has a speed of 5.27 m/s. Calculate size of the force with which the M pushes on the hoop when M is at an angle of 27.0 degrees. Picture attached at the...
45. ### Spring Propels Two Blocks Up Two Ramps

You are right, I read the question incorrectly. Which is a little ridiculous considering I retyped it all out. Taking that into account, this is what I came up with, however this is also incorrect. A) E B) E C) L - Potential energy is mgh, and would I be correct in assuming PE for both should...
46. ### Spring Propels Two Blocks Up Two Ramps

Homework Statement A spring of negligible mass is compressed between two masses on a frictionless table with sloping ramps at each end. The masses are released simultaneously. The masses have the same volume, but the density of M1 is greater than that of M2. G-Greater than, L-Less than...
47. ### Positioning a Third Mass So That It Experiences No Net Gravitational Force

I got it! Thank you so, so much! You were right, I did make a typo entering my numbers into my calculator. I looked back through my workings and found that I had 47.9 instead of 47.4 in one of the M1's by mistake. Thank you! And most importantly, after going over everything so many times I...
48. ### Positioning a Third Mass So That It Experiences No Net Gravitational Force

Which value did you use for M1? I took 47.4 as M1, plugged it into the second equation, and ended up with x = 199.6 m and x = 40.3 m, neither of which were correct. Did I mangle the formula somehow?
49. ### Positioning a Third Mass So That It Experiences No Net Gravitational Force

Since you seemed curious: for my online assignments, I generally get a week to 10 days to complete them. If I get stuck, I can go to my prof or the math help center or other students etc and work through the questions. I get 10 tries to get a long answer question. If If I get one wrong 10 times...
50. ### Positioning a Third Mass So That It Experiences No Net Gravitational Force

It's a loncapa assignment, actually. My prof posts my weeks work to do and I have until the deadline to get my questions done. All my other questions are completed correctly, and I still have an hour and a half, it's just this one question that's messing me up, haha. I understand not...